Fix `Instantiator` service injection so that services of type `ServiceRegistry` can be injected into instantiated things. This was previously available for services created by the `DefaultServiceRegistry`.

Also disallow registration of services of type `ServiceRegistry` so that the automatically provided instances are always used.

Fix `Instantiator` service injection so that services of type `ServiceRegistry` can be injected into instantiated things. This was previously available for services created by the `DefaultServiceRegistry`.

Also disallow registration of services of type `ServiceRegistry` so that the automatically provided instances are always used.

Fix `Instantiator` service injection so that services of type `ServiceRegistry` can be injected into instantiated things. This was previously available for services created by the `DefaultServiceRegistry`.

Also disallow registration of services of type `ServiceRegistry` so that the automatically provided instances are always used.